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From "Grader, Matt - AES" <Matt.Gra...@itt.com>
Subject [users@httpd] Apache Performance Issue
Date Wed, 02 Feb 2005 16:23:45 GMT

Hello,

We have observed several bizarre performance issues with Apache that I am hoping someone out
there has experienced, and can detail the root cause of the problem and what steps are needed
to correct it.

We have noticed poor performance from several different machines running older versions of
IE (usually IE 4 or 5 but sometimes IE 6).  On these machines and browser configurations 
(and only these) every 4th – 5th page request hangs.  A page that loaded fine five minutes
ago may hang now – there is no consistently in what pages hang.   The page usually partially
loads and then stops loading for 2 up to 8 minutes at which point the page will continue loading
until completion.   Our pages are very small (around 200k for html + images) and the machines
we tested each had a broadband connection (Using Firefox the pages load in around 5 seconds).

Our configuration was Apache 2.0.44 with SybPerl 1.2 (an old Sybase perl application).

We have done the following trying to discover the root cause:

1.	Add logging to our SybPerl scripts.  We found that during a hang, the script executes successfully
and in a normal amount of time (less than 2 seconds)
2.	Examined the Apache logs and increased the loglevel.  During a hang Apache does not log
either an access or error (even though from our SybPerl logs we know the script is called
and fully executes).  At the highest reporting loglevels we see the following error:
[info] (32)Broken pipe: core_output_filter: writing data to the network

3.	Packet Sniffed the connection.  When the client sends a request and hangs, it sends the
first request successfully and opens a connection (tcp three way handshake).  This connection
eventually dies and the client sends a new request several minutes later (2-8 minutes) and
then fully loads the page.  We did detect ICMP messages being sent when a hang occurs, but
these are blocked by our firewall (which our Network Administrator assures me is normal for
security reasons).

We have noticed that two things will resolve the issue:

1.	In the internet settings of the computer experiencing the problem, disable HTTP 1.1 and
use HTTP 1.0 instead. No hangs occur.

OR

2.	Roll back Apache to v1.3 (the latest) from our original 2.0.44.

At the moment we have resolved the problem by rolling back Apache, but we would still like
to migrate to Apache 2 sometime in the future.  If you  have any constructive ideas / suggestions
your help would be greatly appreciated.

Thanks.

Matt
matt.grader@itt.com


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